Condensation, Damp and Mould

Damp can cause mould on walls and furniture and make window frames rot. Damp houses encourage the growth of mould and mites. Mites feed on mould and can increase the risk of respiratory illnesses in some people.

There are four main types of damp that can affect your home. The one you need to watch out for the most is condensation.


Condensation is the biggest cause of damp in the home. It is caused when water vapour or moisture from inside comes into contact with a colder surface, like a window or wall. The resulting water drops (condensation) can then soak into your wallpaper, paintwork or even plasterwork. In time, these damp areas attract black mould. 

Condensation mainly occurs during the colder months, and can happen if it is rainy or dry. It is usually found in the corners of rooms, north facing walls and on or near windows. It is also found where there is poor air circulation, such as behind wardrobes and beds, especially if they are against external walls.

Condensation and Mould Growth

Most homes are affected by condensation at some point, but certain activities can increase the problem. It is something that you can put right without expensive work or treatment. 

Cooking, washing, drying clothes indoors, even breathing - all produce water vapour that can only be seen when tiny drops of water (condensation) appear on colder surfaces. 

Turning up the heating will not sort out the problem. 

The first sign of a problem is water vapour condensing on windows and other cold surfaces, and which takes a long time to disappear. This then allows surfaces to become damp.

The second indication is black mould patches growing on damp areas. 

Mould needs four things to thrive:

  • moisture
  • food - such as wallpaper or emulsion paint
  • the right temperature
  • oxygen

If you deal with these issues, you will automatically deal with the mould. 

Warmth versus Ventilation

By opening windows and ventilating your home, you are letting warm moist air escape and letting cool dry air in. It is cheaper to heat dry cool air than it is to heat warm moist air!

If you have window vents, use them. Open your windows slightly for a short period of time - between 30 minutes and one hour. Don't leave your windows open all day.

Six Steps to Reducing Condensation and Mould Growth

1. Produce Less Moisture

Daily activities produce a lot of moisture.To create less moitsure in your house:

  • dry clothes outdoors if possible. Avoid drying clothes indoors or if you have to, dry them on a clothes airer in the bathroom with the door closed and either an extractor fan on or a window slightly open. Vent tumble driers to the outside (never into the home) or buy a condensing type.
  • Cover pans when cooking and do not leave kettles boiling.
  • Do not use paraffin or gas bottle heaters. They produce large amounts of water vapour and are very expensive to run.

2. Remove Excess Moisture 

Wipe the windows and window sills of your home every morning to remove condensation. This is especially important in the bedroom, bathroom and kitchen - opening the window is not enough. 

3. Heating

When it's cold, the best way to keep rooms warm and avoid condensation is to keep a low background heat on all day. Good heating controls on your radiators, a room thermostat and a timer will help you control the heating throughout your house and help manage heating costs. Think about insulation (roof, cavity –wall or external wall insulation), draught-proofing windows and doors, and installing double or secondary glazing.

4. Ventilation

It is important to remove condensation and excess moisture by ventilating rooms. You can ventilate a room without making it draughty or cold. Just open the window slightly or use the window vent. This allows warm, moist air to escape outside and lets cool dry air in. 

Ventilation tips: 

  • Always ventilate or open a window when using the kitchen or the bathroom and close the doors to stop moisture in the air from spreading to other parts of the house. Continue to ventilate these rooms for a short time after a shower, bath or cooking and keep the door closed
  • Open bedroom windows for up to one hour as soon as you get up 
  • Clear window sills of clutter that restricts opening the window and stops surfaces getting wiped
  • Leave space between the back of furniture and cold walls for air to circulate
  • Ventilate cupboards and wardrobes, and avoid overfilling them as this prevents air circulating
  • Do not completely block chimneys and flues – fit an air vent and make sure any gas appliances have the ventilation they need. 

5. Insulation

Insulating and draught-proofing will help keep your home warm and save money on your heating bills. 

  • Insulate the loft to a depth of 300mm
  • Consider secondary or double glazing
  • Consider cavity wall insulation or internal dry lining
  • Draught-proof windows and external doors. When draught-proofing, do not block permanent ventilators or rooms that need ventilation
  • Find out if you can get a grant for insulating your home, this may help lower your bills.

6. Dealing with Mould

Mould can grow on walls, ceilings, furnishings, clothes and toys. 

To kill and remove mould: 

  • Remove mould with a damp cloth and throw away afterwards. Or if possible use a vacuum cleaner and empty afterwards. Do not brush mould as this releases spores into the air.
  • Wipe down the area using a fungicidal wash or diluted bleach. (Use rubber gloves and wear safety glasses).
  • After treatment paint with a fungicidal paint – do not paint over using an ordinary paint as mould is likely to grow back.
  • Dry clean mouldy clothes and shampoo carpets.
  • Regularly check under divan bed drawers, behind wardrobes, bedside cabinets, bedheads and clothing stored in cupboards.

Dealing with condensation and mould growth is not easy. You need to do as much as possible every day. Once a balance has been achieved your situation should improve over time. 

Landlord responsibilities

Landlords should:

  • Work with tenants to find out the cause of the problem.
  • Carry out repairs to make good any defects identified at the property.
  • Redecorate after treatment and use specialist bathroom or kitchen paint, or wallpaper paste with an anti-fungicidal additive.
  • Avoid using wallpaper in bathrooms and kitchens.
  • Supply ventilation with a humidity sensor.

If you are renting a property and the landlord is not fixing a problem you can report it to us using the Rented property in disrepair form.

Other types of damp

Penetrating Dampness 

This type of dampness is usually found on external walls or due to roof leaks on ceilings. It only appears because of a problem outside the home. For example, missing pointing, cracked rendering, missing roof tiles or faulty guttering and pipes. These problems allow water to come through the walls to the inside surfaces. Penetrating dampness is far more noticeable after rain. It looks like a well defined damp-patch which feels damp to touch.

Black mould is rarely seen on areas of penetrating damp. The affected areas are usually too wet and the dampness contains salts picked up when passing through the wall, which prevent the growth of black mould.

Defective Plumbing

Leaks from water and waste pipes in bathrooms and kitchens, are relatively common. Affected areas look and feel damp to the touch and stay damp whatever the weather conditions outside. You will find the source of the problem if you look for issues around:

  • the water and waste pipes that serve the kitchen and bathroom,
  • the seals around the bath, shower and sinks,
  • the external pipework, such as guttering.

Black mould is rarely seen with this type of dampness. The area is usually too wet and the chemicals in the water will prevent mould growth. 

Rising Damp

This is generally caused by water rising from the ground into the home. The water gets through or around a broken damp proof course (DPC) or passes through the natural brickwork if the property has no DPC. Rising damp usually only affects basements and ground floor rooms. It normally rises 12 to 24 inches above ground level and usually leaves a tide mark low on the wall. You may also notice white salt marks on the area. 

Rising damp will be present all year round, but is more noticeable in winter. If lit's not treated, it can cause wall plaster to crumble and wallpaper to lift. 

Black mould is not usually seen where there is rising damp. This is because rising dampness carries with it ground salts which prevent the growth of black mould.